Tascja

03-15-2008, 12:39 AM

ok, i have this question and i'm a quite bit lost because i can't find the rule in my textbook about .5 being substituted. any help would be greatly appreciated. it goes like this...

If nothing is known about the p, 0.5 can be substituted for p in a sample size formula for a population proportion. But when this is done, the resulting sample size may be larger than needed to construct a confidence interval.

Under what circumstances will using p=0.5 in the sample size formula yield a sample size larger than needed to construct a confidence interval for p with a specified bound and a specific confidence interval?

Thank you so much!

If nothing is known about the p, 0.5 can be substituted for p in a sample size formula for a population proportion. But when this is done, the resulting sample size may be larger than needed to construct a confidence interval.

Under what circumstances will using p=0.5 in the sample size formula yield a sample size larger than needed to construct a confidence interval for p with a specified bound and a specific confidence interval?

Thank you so much!